The present invention relates broadly to an authentication system, and in particular to an electronic authentication system for verifying the security of a remote transmitting station.
In the prior art there are many situations where it is necessary to verify the information or data passing between terminals that are remotely located from one another. Such is the case where an unattended remote station is controlled by a manned central station that is coupled to it by a communication or hard-wired link. In order to secure the system against unauthorized persons exercising control over the remote station by either gaining access to or tapping into the communications link, it is necessary that the security of the remote station be verified by the main control station. A specific example is the recent development in the banking industry where an unattended remotely located branch station may dispense cash to verified depositors in the form of withdrawals or loans under the control of a main or central bank. In such a system a depositor or customer establishes his identity at the branch station through a credit card verifier or the like and communicates the amount of money desired to the central bank. If his balance or credit is sufficient an attendant at the central bank then transmits a command signal to the branch system which initiates the operation of the cash dispensing mechanism. In a system of this type it is obvious that absolute security is essential, since otherwise a skillful criminal could tap into the communications link, learn the command signal, and rapidly empty each branch station of its cash stock by simply duplicating the signal. The prior art approach to this problem has been either the coding of the command signal and or camouflaging it, such as by mixing or interweaving it with an accompanying data or information signal. One of the drawbacks to this approach is that both the code and the camouflaging pattern are always fixed and invariant, and they therefore may be broken or compromised by repeated monitoring and comparison.